Fix another TypeScript parsing edge case (#4248)

This fixes a regression with a change in the previous release that tries to more accurately parse TypeScript arrow functions inside the ?: operator. The regression specifically involves parsing an arrow function containing a #private identifier inside the middle of a ?: ternary operator inside a class body. This was fixed by propagating private identifier state into the parser clone used to speculatively parse the arrow function body. Here is an example of some affected code:

class CachedDict {
  #has = (a: string) => dict.has(a);
  has = window
    ? (word: string): boolean => this.#has(word)
    : this.#has;
}

Fix a regression with the parsing of source phase imports

The change in the previous release to parse source phase imports failed to properly handle the following cases: